Electric water heater of the storage type



Dec. 31, 1946. A, R, DRAFFlN 2,413,6l

ELECTRIC WATER HEATER OF THE STORAGE TYPE Filed Dec. 2S, 1944 Patented Dec. 31, 1946 2,4l3,5ll

ELECTRIC WATER HEATER OF THE STORAGE TYPE I Arthur Robert lDraiin, Camberwel, Melbourne, Victoria, Australia Application December 26, 1944, Serial No. 569,840 In Australia December 13`, 1943 This invention relates to electric water heaters of the storage type, designed to provide for a substantially continuous supply of hot water for domestic and other purposes and more especially to such installations which operate upon electric current supplied on an oi peak or restricted hour tariff (sometimes known as night heating) and under a higher or ordinary domestic, comercial or industrial tarii (sometimes known as day heating).

So far as concerns the manner of generating and delivering the hot Water, such storage heaters may be said to fall into two main classes, i. e. those `which operate upon the displacement or pressure principle according to which cold water is fed into the bottom of the storage chamber and hot water is taken oil from the top, and those which operate upon the falling level or spill over principle according to which the hot water is delivered o1' drawn olic from near the bottom of the storage vessel.

I consider that the displacement or pressure principle is to be preferred for various reasons, primarily in that it provides a better operating efficiency, which is of paramount importance. In addition, there is the physical advantage that the storage vessel of a displacement or pressure type heater may be installed in practically any position such as under the floor, on the floor, in a cupboard, or in the roof of a building, Whereaswth the falling level type of heater, the storage vessel requires to be elevated above the highest draw onq point or tap of the system.

There are numerous types of heaters which operate upon the aforesaid displacement or pressure principle. The salient features of the four main types of such heaters will now be briefly described as `such description. will assist a better understanding of the present invention and the important advances which arise therefrom.

Type A.-According to this type a circulation electric heater is arranged externally of the storage vessel and progressively heats all oi the water in the latter by a circulation of the water from the bottom of the vessel through the heater and into the top of the vessel. Satisfactory results are obtainable when operating upon a continuous heating tarii but it is found when operating during the oli-peak or restricted hour period there is a very great difference in temperature between the hot water at the top of the vessel and the `water at-the bottom or the vessel, at the end ol the heating period. Thus when hot water is being drawn oil and the electric current is f 11 Claims. (Cl. 219-39) switched orf, the diierence in temperature is most noticeable and low temperature water is likely to be drawn off ata comparatively early stage. In cases where a thermostat device is tted, it is located near the bottom of the storage Vessel but such device is ofno practical use when operating upon the ordinary tariff unless it is desired that the entire body of water should be heated.

Tyre B- According to this type an electric heating element is immersed in the water near the bottom of the storage vessel and heats the entire body o1" water during the off-peak or restricted hour period. Notwithstanding the use of a throw-over switch for replenishment when operating upon the ordinary tariii, a long delay occurs before hot water at a desirable temperature is available for drawing off. This delay is due to the fact that the element has to transmit its heat into the main body of water and thus, all of the water has to be heated before any hot water can be drawn on. Similarly to type A, type B is frequently fitted with a thermostat device near the bottom of the vessel, but this device switches off the current only when the whole of the storage vessel has been heated.

Type C.-According to this type, two separate heating elements are employed, one -being immersed in the water at or near the botto-m of the vessel and the other element, usually known as an upper or booster element, is arranged within the vessel near the top thereof and is intended to replenish the supply of hot water at the upper part of the vessel to meet an urgent demand. If the quantity of water above the upper or booster element amounts to say l0 gallons then, while the installation represents an improvement upon types A and B, it suffers from the disability that it does not make sufficiently hot water available for drawing off until substantially the whole 1D gallons of water has been heated throughout. In this type, a thermostat device is tted near the bottom of the storage vessel to control the heat during the oil-peak or restricted hour period, but the upper or booster element is either switched on or oli by hand, or if it is desired to be rendered automatic in operation, then an additional thermostat has-to be tted.

Type D..-In this case a heating element is immersed near the bottom -of the vessel and is so arranged that a proportion of the heat is transmitted. into the main body of water, while the remainder of the heat is transmitted to a confined body of water which passes by way 'of an external tube to the top of the vessel. The heating element, when operating under the restricted hour tariii heats the whole of the water in the storage vessel although there is a slight temperature variance between the top and the bottom at the conclusion of the heating period. When the supplt7 of hot water approaches exhaustion during daytime use, replenishment of hot water is effected by operating a throw-over switch whereupon the electric current is charged for at the ordinary tariff. A proportion o-f the heated water is delivered to the top of the storage vessel readyV for drawing oir, but a considerable proportion ofj the heat is still transmitted direct tc the main body of water. Thus, while this type represents an improvement over the previously mentioned types, it still does not replenish hot water at the top of the vessel with suiiicient rapidity. It is customary to provide a. thermostat device near the bottom of the vessel for automatically switching cif the current when the entire body of water has been raised to a given temperature. This is'eiiective for the ofi-peak or restricted hour tariff heating but if the current is carelessly'or otherwise left switched on after replenishing the supply of hot water duringoperation upon the ordinary tarii, the thermostat will not switch off the current until the entire body of water has been heated to the predetermined temperature notwithstanding that only a relatively small amount of hot water may be required for immediate use. This is, of course, wasteful and uneconomic.

The present invention aims to overcome the foregoing disadvantages and disabilities in a simple and practical manner and to provide for the utmost efficiency, convenience, reliability and economy in the operation of storage heaters of the kind in question.

' More speciiically the invention, while employing only a single heating element and a single thermostat control device, provides for the entire body of water to be heated to an even temperature throughout, which is ideal especially when operating on the off-peak or restricted hour tariff, and also provides, as and when required, for the most rapid replenishment of hot water at the top of the storage'vessel so that it becomes readily available to meet a sudden demand or emergency.

In order to accomplish this and certain other desirable objects as' will be explained more fully hereinafter, I employ a single heating element of the water circulating type and connect it with a hot water storage vessel and in a water ow circuit which includes a hot water control valve or diverter device.V In one condition this device directs the heated water from the circulatory heater into the lower part of the storage vessel so that the entire body of water is gradually brought to a desired temperature, and, in another condition, diverts all of the heated water from the heater directly into the top part of the vessel, so that hot water is almost instantaneously or, at least, very quickly available at any draw oi tap of the system, notwithstanding that the major portion of the water in the vessel is cool or well below a desirable high temperature.

The water control valve o-r diverter device is preferably arranged to be brought into action automatically upon switching over to operation upon the ordinary tarii, while a single .thermostat deviceis arranged to exercise control over the heating element at all times, i. e. whether it is operating under the oir-peak (night-time) tariii or A ordinary (day-time) tarii.

VThe above and various other objects, features and advantages of the invention will now be described with reference to one practical embodiment illustrated in the accompanying drawing in Which- Figure 1 is a vertical elevation, partly in section.

Figure 2 is an enlarged sectional elevation of the hot-water control valve or diverter device and associated parts.

An installation in accordance with the invention includes a cylinder or vessel 2 of appropriate capacity to serve as a hot water reservoir. This vessel is surrounded by a lagging 3 of appropriate heat insulation material and has a cold water inlet ll at its bottom connected with an overhead cold water supply tank (not shown) which, as usual, may be fitted with a ball-cock device or the like.

A single electric heating element 6 of the water circulating type is located in any suitable position preferably immediately beneath the bottom of the sto-rage vessel. The heating element casing 'I is surrounded by a jacket 8 one end of which is connected by a pipe 8a with the bottom of the storage vessel near the point where the cold feed water enters the vessel. A baiile (not shown) may be provided within the lower part of the vessel to prevent the incoming feed water from mixing with the hot water in the upper part of the vessel.

The heater water jacket 8 should be inclined slightly towards its other or outlet end from which a pipe or conduit 9 extends upwardly and may be said to have three branches. One branch I0 leads horizontally into the storage vessel at a relatively slight distance above the bottom thereof. A second branch II continues vertically upwards and enters the top of the storage vessel preferably adjacent the hot water outlet 2a which may have the usual exhaust pipe (not shown) associated therewith. The third branch I2 extends horizontally outwards in alignment with the iirst branch and is connected to the water control valve or diverter device I3 as best seen in Figure 2. These three pipes or branches should extend through the heat insulating material 3 around the storage vessel so as to avoid dissipation of heat.

As illustrated, the device I3 comprises a relatively small capacity water chamber I4 into the upper part of which the third mentioned branch I2, or a tail piece I2a connected thereto, opens. Around the exterior of the lower part of this water chamber there is clamped a relatively low wattage electric hea-ting coil I5, suitably insulated, and which may be adapted to be energised only when the installation is operating under the ordinary tariff. In such cases this heating coil may be operatively connected with a throw-over switch.

Retained within the lower part of the chamber I4 is an expansible bellows I8 containinga suitable quantity of an appropriate substance'which has a high rate of expansion when subjected to heat. Upstanding from the head or top of these bellows is a rod I'I connected by a pivoted bell crank lever I8 with a horizontal rod I9 extending from a plunger Zlwhich is disposed in the third branch I2 and has a tapered or conical nose 2| adapted to make contact with a correspondingly shaped seating 22 in the first branch I0. 'A spring 23 may be associated with the before-mentioned parts in order to yieldingly oppose' expansion of the bellows device and to retract the plunger 20' from the seating 22 of branch Ill. 'I'he plunger should be .a good sliding t within kthe third branch but it is preferably tapered away as at 24 and has an end portion or `tail piece 24a of nor- Only one thermostat control device is required according to this invention, and such device, which may be: of any suitable form. and suitably connected in the electric circuit, is ,preferably located within a tube 25 closedv at its inner end andv projecting horizontally into the vessel at a relatively short `distance from the top.

Whenthe installation is in use under the. oirpeak tariff the`v plunger 20 will, by reason of the spring` 23 and the collapsed condition of. the bellows ITS, be withdrawn from the seating 22 in branch pipe Ill' as seen in unbroken lines in Figure'f2. Thus; hot water fromvthe. heatingelement jacket will flow through branchv I into the lower portion of the. storage vessel so that the entire body of water therein will be gradually brought up to a substantially uniform temperature. When this has been eiected to the required temperature, the supply of electric current to the heating element will be automatically cut-off. by the thermostat device. y

If and when the supply of hot water in the storage vessel has become exhausted or is :approaching exhaustion and hot water is urgently required at `any draw-01T point in the system., as may frequently happen in day-time, then the low Wattage heating coil is brought into action. The heat produced by this coil rapidly heats the water in the chamber I4 and when such water reaches a suitable- `temperature the bellows de'- vice I6 expands, and, through medium of the aforesaid rods and lever, moves the plunger 20 along the third. branch I2v so that the cone or like, Shaped nose 2| of the plunger contacts with By tapering the plunger asaforesaid and ar ranging for such tapered portion to come adjacentjthe upper end of pipe 9, there is a desirable restriction in the pathway for the hot water which ensures it reaching the top of the vessel at the desired temperature. advantages in. adopting such method of restriction, in relation to the usual method of requiring the Water to pass through a small xed orice or hole. Thus, there is no likelihoodv of Athe restricted pathway becoming blocked by foreign matter in the water, and any' matter that may be deposited `around the pathway will be removed by the movement of the plunger.

When the throw-over switch is returned to the off-peak position, the low wattage heat coil is simultaneously switched oiT so that the water in' cham-ber I4 will cool and .the `pressure of the contained chemical or other substance in the bellows will be reduced so that the associated spring 23 will force the bellows back to normal and at the same time cause the plunger to be withdrawn Vfrom the seating at the inner end of the branch I0 .whereby direct communication is re-estabw lished between the heating elementaiacket and the-lower part of the storage vessel. If thethrow-over switch is left on' in the normal ,tarii position, then the current supply tothe heating element will be automatically switched kof! -by the thermostat device aftera predetermined quantity of hot water has accumulated in There are several Y the upper part. of the storage vessel. After an interval of time the thermostat. will again switch onthe'current where the water surrounding it has `dropped appreciably in temperature. This automatic. switching on and off action will be repeated until eventually all the water is heated.

It will be. apparent from the foregoing that the invention permits of full advantage being taken of botlr off-peak and normal. tariffs and, -by virtue of the hot water control valve or diverter, enables hotl water to be obtained at any time at any draw oi pointin .the system without wastage of electric current, in a; most economical way in that such hotl water is delivered. directly from the heating element jacket into the top of the storage vessel.

In addition to the ability to quickly replenish the supply of hot water at ordinary tariff, the di'- verter device also enables, if it is so desired a portion only of the water to be heated at the offpeak or restricted hour tariil. This is eiected by moving the usual throw-over switch to the oipeak position and switching the low wattage heating coil I5 into circuit. Thereupon the water in the upper part of the storage vessel will be heated and as soon as it has reached the desired temperature the thermostat will automatically cause the current to the heating element to be initially switched off.

It will be noted that a small diameter pipe 26 leads from pipe 9 into the water chamber I4 and that another small diameter pipe 21 leads from the rear part of pipe I2 upwardly into pipe II. The primary purpose of the pipes 26, 21 is to prevent steam accumulation and overheating ofthe water in chamber I4 when the coil I5 is switched on, Under such condition, and with the plunger 'moved onto its seating, the two pipes provide for a small by-pass or circulatory iiow of hot water from pipe 9, through pipe 26 the chamber I4 and pipe 21, into pipe II. The tail piece 24a of the plunger will, at this stage, be located between pipe 21 and branch I I as indicated by broken lines in Figure 2.

Until the tail piece 24a moves to the right past pipe' 21 as aforesaid there will not be any circulation of hot water through chamber I4 and this is an advantage as it will lead to quick heating of thewater in chamber and a quick movement of the plunger against seating 22.

It is to be understood that the construction of the hot water control or diverter device I3 may be varied in many respects. For instance, the heating coil I5 could be replaced by a solenoid appropriately connected in the electric circuit and arranged to actuate the plunger 20 or other suitable valve through suitable linkage, upon operation of the change over switch. Alternatively, a plunger or other suitable valve could be adopted for manual operation.

Having now described my invention what I claim as new and desire to secure by Letters Patent is:

l. In a water heater of the storage type suitable for operation under the off-peak and the ordinary tariffs of electric supply, a hot water storage vessel, a heating element of the water circulating type having a water inlet connected with the lower part of said vessel, a thermostat control. device for said heating-element, andra water flow circuit extending between a hot water outlet of said heating element and upper and lower hot water inlets of said vessel, said circuit having interposed therein the controldevice which, selectively, directs heated water 4exclusively from the heating element into the lower part of said vessel softhat the .entire body of watertherein.. is gradually raised to a desired even temperature through-.- out or exclusively directs all of the hot. water from the heating element into the top part of the vesselso as to effect a rapid development of hot Water for immediate withdrawal. 1 Y

2.*In a Water'heater, as claimed inv claim l, wherein said water ow circuit includes a pipe extending upwardly from the hot water outlet of said heating element, a first branch extending from said pipe into the lower part of the storage vessel, a second. branch extending into the top of the storage vessel, and a third 'branch .for interconnecting said rst and second branches, a valve member being provided and selectivelyoperableto.; cut 01T exclusively communication between the rst branch'and the second branchmaintaining the iirst branch open to said pipe, or to exclusively cut off communication between said pipe and the rst branch to cause the pipe to communicate with said second branch. 1

3. In a water heater, a combination as claimed in claim 1, wherein said control device includes a relatively small capacity water chamber con-i nected in saidflow circuit and heated by a relatively low wattage coil, a heat expansivebellows in said chamber, a valve for .controlling the ilow of hot water from said heating element exclusive-v ly to the lower part Vor to'th'e top of said'vessel, and operative connection between'said bellows and said valve.

4. In a water heater, a combination as claimed in claim 1, wherein said control device includes a relatively small capacity water chamber connected in said ilow circuit and--heated by a re1- atively low wattage coil, a heat expansive bellows in said chamber; a valve for controlling the flow of hot water from said heating element exclusively to the lower part or exclusively toA the top of said Vessel, and operative connections between said bellows andA said valve, saidv bellows being retained within said water chamber with its upper free end connected to a rod carrying said valve'member.

5. In va water heater, a combination as claimed in claim 1, wherein said water flow circuit in cludes a pipe extending upwardly from the hot Water outlet of' said heating element, afirst branch extending from said pipe into the lower part of the storage vessel, a second branch exf tending into the top of the .storage vessel, and a third branch interconnecting said rst and second branches, a valve member being provided and operative selectively to exclusively cut off communication between the rst branch and the second branch while maintaining the rst branch open to said pipe, or to exclusively cut off communication betweensaid pipe and the first branch and maintain the pipe in communication with said second branch by way of said third branch, said valve member including a plunger having a tapered portion to restrict communication .between said pipe Yleading from the heating element and said second branch when the valve isin one selected position. a

.6. In a water heater, a combination as claimed in claim l, wherein said water ow circuit in-` cludes a .pipe extending upwardly'from Ythe hot water outlet of said heating` element, .a rst branch `extending. from said pipe into the lower part of the storage vessel, a secondvbranch ex-l tending into the top of the storage vesseL'and. a. thirdbranch for interconnecting said rstv and second branches, a Valve member selectively operableA to exclusively vcut on" communication betweenthe iirst branch and the second' branch while maintaining the rst branch open to'said pipe, or tor exclusively cut off communication between said pipe and the iirst branch while maintaining the pipe in communication with said second branch by Awayof said third branch, said valve 'member including( a plunger having' a tapered portion to 'restrict communication'between said pipe leading from the heating element and said second branch when the valveis in one selected position, said plunger having a tail piece of normal'diameter spaced rearwardly from said tapered portion. Y 7. A water heater as claimed in claim 1, wheres inv said hot water control device' is opera-blebto direct hot `water exclusively into the'top ofthe storage vessel automatically upon the operation of a switch for changing over from olif-peak tariii to ordinary tariff.

8. A water heater as claimed in claim 1, wherein said heating element is located adjacent the bo-ttom of said vessel, and wherein said thermostat device is positioned within the upper part 9. An improved water heater of the storage type, including a hot water storage vessel, a heating element located beneath the vessel and disposedxwithin a casing; a water jacket sur: rounding said casing, an inletpipe 'extending froml the lower part oi the vessel into the one end of saidjacket, a hot water outlet pipe lead-f ingupwardly' from the other'end of said jacket, a first branch extending from said outlet pipe into the lower part of the vessel, a second branch extending from said outlet'pipe into the top of the storage vessel and a control device .operative selectively to place vsaid hot water outlet pipe into exclusive communication with said rst branch or with said second branch as may be desired. f 1

10. An improved Water heater asl claimed in claim 9, wherein a thermostat device isarranged within-and at an appropriate distance beneath the top of said storage vessel and is operatively connected with said heating element so as to control its operation irrespective of theselected positions of saidcontrol device. Y

11. In a water heater, a combination as claimed in claim '1, wherein said controldevice includes a relatively small capacity water chamberconnectedin said iiow circuit to be' heatedby a i., relatively low wattage coil, a heat expansive bel- 'and said water chamber vand another relatively small diameter pipe for-establishing communication'between said chamber and the top part of said storage vessel'when said control device is in one selected position.

ARTHUR ROBERT -DRAFEiNL- 

